The dehydrogenation of 1,4-cyclohexadiene (1) cis-3,6-dimethyl-1,4-cyclohexadiene (2) and trans-3,6-dimethyl-1,4-cyclohexadiene (3) with triphenylmethylfluoroborate in acetonitrile or 2,3-dichloro-5,6-dicyanobenzoquinone (DDQ) proceeds in the same reactivity sequences 2 > 1 > 3. The mechanism of the dehydrogenation of 1,4-cyclohexadienes with triphenylmethylfluoroborate and DDQ is discussed in the light of these results and in view of the kinetic isotope effects.